You can run the ESXi 5.0.x installer from a CD/DVD or USB flash drive to do an interactive upgrade or migration. This method is appropriate for deployments with a small number of hosts. The installer works the same as for a fresh installation, but if you select a target disk that already contains an ESX/ESXi 4.x or ESXi 5.0 installation, the installer upgrades or updates the host to 5.0.x, and gives you the option to migrate some existing host settings and configuration files, and preserve the existing VMFS datastore. See Upgrade or Migrate Hosts Interactively.

Perform a scripted upgrade or update

You can upgrade or migrate hosts from version 4.x ESXi and ESX and update version 5.0 ESXi hosts to ESXi 5.0.x by invoking a script, for an efficient, unattended upgrade. Scripted upgrades and updates provide an efficient way to deploy multiple hosts. You can use a script to upgrade or update ESXi from a CD, DVD or USB flash drive, or by PXE-booting the installer. You can also call a script from an interactive installation. See Installing, Upgrading, or Migrating Hosts Using a Script.

vSphere Auto Deploy

Auto Deploy is a new feature in vSphere 5.0. Working with hosts managed by vCenter Server, Auto Deploy loads the ESXi image directly into the host memory, rather than installing it on the host hard disk. You cannot use Auto Deploy to upgrade or migrate version 4.x ESX and ESXi hosts to ESXi 5.0, because version 4.x ESX and ESXi hosts are deployed by the traditional method of installing the software on the host hard disk. After a ESXi 5.0 host is deployed with Auto Deploy, you can use Auto Deploy to upgrade, update, or apply patches to the host. To do this, you reprovision the host by rebooting it with a new image profile that contains the ESXi upgrade, update, or patch, a host configuration profile, and, optionally, third-party drivers or management agents provided by VMware partners. You can build custom images by using ESXi Image Builder CLI. See Using vSphere Auto Deploy to Reprovision Hosts.

esxcli

You can apply patches to ESXi 5.0 hosts using the esxcli command-line utility for ESXi. You cannot use esxcli to upgrade ESX/ESXi 4.x hosts to ESXi 5.0.x. This utility requires the vSphere CLI. See Upgrading Hosts by Using esxcli Commands.

The esxupdate and vihostupdate utilities are not supported for ESXi 5.0.x upgrades or updates.